NASA study shows aircraft technologies that increase energy efficiency nearly 50%

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A suite of technologies now in development can deliver a new airliner by 2025 that is 40-50% more energy efficient and generates 30-40dB less noise, according to results of a NASA study released on 11 January.

NASA last year funded three contractors - Boeing, Lockheed Martin and Northrop Grumman - to each develop new airliner concepts that could enter service around 2025 specifically designed to meet a set of ambitious targets for emissions reductions.

If current budget plans survive, NASA's aeronautics branch hopes to select one of the designs to produce a 737-sized subscale test vehicle in 2016, with the ultimate goal of proving the technologies required for a new, 767-sized cargo or passenger aircraft as early as nine years later.

"We envision this vehicle to be used to move the state of the art along in the use of composites," said Fay Collier, manager of NASA's environmentally responsible aircraft programme.

Each of the aircraft makers compared how new airframes, structures, engines and aerodynamic techniques can cut down emissions between an advanced "tube-and-wing" and a more radical design.

In the latter category, Boeing studied two different kinds of blended wing bodies powered by either three open rotors or two advanced turbofans. Northrop studied a flying wing resembling a scaled-up version of the B-2A bomber with embedded propulsion. Lockheed's designers considered a boxed-wing twinjet.

Although the studies proved the advanced concepts would be more efficient and quieter, the same technologies applied to conventional tube-and-wing airframes are also very effective.

NASA's study focused on applying new techniques to improve laminar airflow, advanced composites to reduce weight, ultra-high bypass engines to create more energy efficiency, new combustors to cut harmful emissions and new ways of integrating engines into the airframe to shield noise levels.

As a result, energy efficiency on a tube-and-wing airframe improved 43%, with one-third of the improvement driven by the engine alone, Collier said.

But the study also showed that the only way to achieve NASA's "N+2" environmental goals is to move to a new airframe configuration. The tube-and-wing concepts fall about 8% short of the energy efficiency target, and up to 12dB short of the noise reduction target, Collier said.